Thermal Biosensors in Biotechnology - Advances in Biochemical Engineering Biotechnology - page 56

toring tool for enzyme catalyzed processes. The common criticism that bio-
sensors are not stable enough for on-line monitoring, is not convincing in the
field of biotransformations,because the enzymes for synthesis also have a lim-
ited process stability. On the contrary, the non-complex biotransformation
media should increase their process stability.
Recently,the ET was presented as an on-line monitor for biotransformation
processes (Lammers and Scheper,1996).Here,three different enzyme-catalyzed
processes of industrial interest were investigated.In the first example,the enzy-
matic production of L -ornithine was monitored via urea analysis. In this pro-
cess, arginase hydrolyzes L -arginine with the release of urea and L -ornithine.
Immobilized urease was set into the ET in order to monitor urea release, and
on-line data informed us of the progress of production.Moreover,a computer-
controlled set-up (Fig. 15) allowed us to remove the product at a nominal value
and to add fresh substrate (Fig. 16).
In further experiments,the ET was shown to monitor enzymatic L -methioni-
ne synthesis via amino acylase. Here, decreasing starting material data ( N -
acetyl- DL -methionine) were of interest.The process was compared with native
and immobilized biocatalyst (Fig. 17).
In a third example,the production offructose was obtained.Here,the starting
material sucrose was hydrolyzed via invertase to fructose and glucose.The pro-
gress in hydolysis was monitored with an ET containing coimmobilized glucose
oxidase and catalase. Following the addition of glucose isomerase, it caused a
shift of ingredients to fructose (Fig. 18).In summary,the connection of enzyme
and (calorimetric) biosensor technology might be very effective for a number of
enzyme catalyzed processes.
Fig.15. Computer controlled set-up for on-line monitoring of enzyme catalyzed processes